CN101903478A

CN101903478A - Coated pipes having improved mechanical properties at elevated temperatures and a method of production thereof

Info

Publication number: CN101903478A
Application number: CN2008801217371A
Authority: CN
Inventors: 马丁·安克尔; 西夫·博迪尔·弗里德里克森; 波尔·克里斯蒂安·本茨勒德; 马茨·贝克曼; 莱夫·莱登; 马尔库·瓦赫泰里; 彼得里·雷科宁
Original assignee: Borealis Technology Oy
Current assignee: Borealis Technology Oy
Priority date: 2007-12-20
Filing date: 2008-12-10
Publication date: 2010-12-01
Anticipated expiration: 2028-12-10
Also published as: US8142871B2; EP2072587A1; RU2446197C2; EP2072587B1; RU2010124688A; AU2008340746A1; CN101903478B; WO2009080212A1; AR069912A1; PL2072587T3; US20100279047A1; AU2008340746B2

Abstract

The present invention deals with coated pipes having a layer of multimodal polyethylene. The multimodal ethylene copolymer is a copolymer of ethylene with one or more alpha-olefin comonomers having from 4 to 10 carbon atoms and has a weight average molecular weight of from 70000 g/mol to 250000 g/mol and a melt index MFR2 of from 0.05 g/10 min to 5 g/10 min, a melt index MFR5 of from 0.5 to 10 g/10 min and a density of from 945 kg/m3 to 958 kg/m3. The coatings have a high stiffness, good properties at elevated temperatures and acceptable stress-cracking properties.

Description

Coated pipe and manufacture method thereof with improved mechanical behavior under high temperature

Technical field

The present invention relates to the polymeric coating pipe, especially, the present invention relates to the coating metal pipe that can under elevated operating temperature, use.In addition, the invention still further relates to the method for making described coating metal pipe with high productivity and good production economy.

Background technology

Disclose among the EP-A-837915 and in the steel pipe coating, used bimodal or multimodal ethylene polymkeric substance.Yet, even the document has instructed described coating to have excellent mechanical property, still need to improve coating under elevated operating temperature performance and/or the coating with higher hardness and acceptable stress cracking performance is provided.

Summary of the invention

The invention provides the metal tube of polyethylene coating, its floating coat has the balance between improved hardness and the anti-stress cracking performance, and/or described metal tube can use under elevated operating temperature.

A first aspect of the present invention provides a kind of pipe that comprises internal surface, outer surface layer (A) and cover the coating (B) of described outer surface layer (A), its floating coat (B) comprises coating composition (B-2), coating composition (B-2) comprises ethene and one or more have the multimodal multipolymer (B-1) of the alpha-olefin comonomer formation of 4-10 carbon atom, the weight-average molecular weight of multimodal ethylene copolymer (B-1) is 70000g/mol-250000g/mol, melting index MFR ₂Be 0.05g/10min-5g/10min, melting index MFR ₅Be 0.5-10g/10min, and density is 945kg/m ³-958kg/m ³

A second aspect of the present invention provides the pipe that comprises internal surface, outer surface layer (A) and coating (B), its floating coat (B) comprises coating composition (B-2), coating composition (B-2) comprises ethene and one or more have the multimodal multipolymer (B-1) of the alpha-olefin comonomer formation of 4-10 carbon atom, and described multimodal ethylene copolymer (B-1) further comprises:

Weight based on multimodal ethylene copolymer (B-1) is the low-molecular-weight ethylenic homopolymer component (B-1-1) of 40-60%, and the weight-average molecular weight of described low-molecular-weight ethylenic homopolymer is 5000g/mol-70000g/mol; With

Weight based on multimodal ethylene copolymer (B-1) is the high molecular weight ethylene copolymer component (B-1-2) of 60-40%, described high molecular weight ethylene copolymer is the multipolymer that ethene and one or more alpha-olefin comonomer with 4-10 carbon atom form, and has the weight-average molecular weight of 100000g/mol-700000g/mol; With

The weight-average molecular weight of described multimodal ethylene copolymer is 70000g/mol-250000g/mol, melting index MFR ₂Be 0.05g/10min-5g/10min, melting index MFR ₅For 0.5-10g/10min and density are 945kg/m ³-958kg/m ³

A third aspect of the present invention provides a kind of method of making aforesaid coated pipe.Said method comprising the steps of:

The have outer surface layer pipe of (A) is provided;

The outer surface layer (A) that coating composition (B-2) is imposed on described pipe is gone up to form coating (B), wherein coating composition (B-2) comprises that ethene and one or more have the multimodal multipolymer (B-1) of the alpha-olefin comonomer formation of 4-10 carbon atom, the weight-average molecular weight of described multimodal ethylene copolymer (B-1) is 70000g/mol-250000g/mol, melting index MFR ₂Be 0.05g/10min-5g/10min, melting index MFR ₅For 0.5-10g/10min and density are 945kg/m ³-958kg/m ³

A fourth aspect of the present invention provides a kind of method that comprises the steps:

(i) at first polymerization stage, polymerization low-molecular-weight ethylenic homopolymer is the Alathon of 5000g/mol-70000g/mol with the preparation weight-average molecular weight in the presence of polymerizing catalyst, hydrogen, ethene and optional inert diluent, and this Alathon accounts for the 40-60% of multimodal ethylene copolymer (B-1) weight; With

(ii) at second polymerization stage, in the presence of the alpha-olefin comonomer of polymerizing catalyst, ethene, at least a 6-10 of a having carbon atom and optional hydrogen and/or inert diluent, carry out polymerization has the alpha-olefin comonomer formation of 6-10 carbon atom with preparation ethene and one or more multipolymer, the weight-average molecular weight of described multipolymer is 200000g/mol-700000g/mol, the 40-60% of this high molecular weight ethylene copolymer ingredients constitute multimodal ethylene copolymer (B-1) weight; And, wherein said first and second polymerization procedures are the successive polymerization step, the polymerisate that any step the preceding obtains is present in subsequently the step, the wherein said first step and second step can be carried out in random order, the weight-average molecular weight of gained multimodal ethylene copolymer (B-1) is 70000g/mol-250000g/mol, melting index MFR ₂Be 0.05g/10min-5g/10min, melting index MFR ₅Be 0.5-10g/10min, and density is 945kg/m ³-958kg/m ³

(iii) reclaim described multimodal ethylene copolymer (B-1);

(iv) obtain coating composition (B-2), it is the multimodal ethylene copolymer (B-1) of 80-100%, preferred 85-100%, particularly 90-99% by weight that coating composition (B-2) contains, optional additive and other optional polymkeric substance;

(v) described coating composition (B-2) being imposed on tube outer surface layer (A) goes up to form coating (B).

Coated pipe of the present invention has excellent anti-stress cracking and high vicat softening temperature, is generally at least 117 ℃ and preferably at least 119 ℃, and high-wearing feature.

In addition, coating composition of the present invention demonstrates high rigidity and high environmental stress crack resistance, and high vicat softening temperature.

The coating process of described pipe makes the coated pipe that makes have the excellent mechanical behavior under high temperature and the rigidity of improvement, still has acceptable anti-stress cracking simultaneously.And described coated pipe can the high productivity manufacturing.

Embodiment

Multimodal ethylene copolymer

Multimodal ethylene copolymer (B-1) has the weight-average molecular weight of 70000-250000g/mol, 0.05-5g/10min, preferred 0.1-2.0g/10min, the more preferably melting index MFR of 0.2-1.0g/10min ₂Preferably, multimodal ethylene copolymer (B-1) also has 0.5-10g/10min, the more preferably melting index MFR of 1.0-5.0g/10min ₅And described multimodal ethylene copolymer has 945-958kg/m ³, preferred 946-956kg/m ³More preferably 946-954kg/m ³Density.

(B-1) has 945-958kg/m when multimodal ethylene copolymer ³, preferred 946-956kg/m ³Density the time, described composition has the rigidity and the high-temperature behavior of expectation.If density is lower than the lower limit of described scope, then the rigidity variation and the favourable high-temperature behavior that can not obtain to expect, for example vicat softening temperature.On the other hand, if density is higher than the upper limit of described scope, then can not obtain enough anti-stress cracking levels.The inventor finds, when polymkeric substance (B-1) is particularly advantageous when to be ethene with one or more have the multipolymer of alpha-olefin formation of 6-10 carbon atom, because use this comonomer can obtain to have the composition of high resistance to stress cracking behavior.

Preferably, multimodal ethylene copolymer (B-1) has wide molecular weight distribution, shows as the ratio M of weight-average molecular weight and number-average molecular weight _w/ M _nBe 15-50, preferred 20-40 and especially 25-40.

Advantageously, based on the amount of multimodal ethylene copolymer, multimodal ethylene copolymer (B-1) comprises and is the low-molecular-weight ethylenic homopolymer component (B-1-1) of 40-60% by weight.Low-molecular-weight ethylenic homopolymer component (B-1-1) has the weight-average molecular weight of 5000-70000g/mol, preferred 15000-50000g/mol.Preferably, low-molecular-weight ethylenic homopolymer component (B-1-1) has 100-1500g/10min, the more preferably melting index MFR of 150-1000g/10min ₂Preferably, described low-molecular-weight ethylenic homopolymer component has 969kg/m at least ³, more preferably 971-978kg/m ³Density.

It should be understood that term among the present invention " homopolymer " is used in reference to the linear tetrafluoroethylene polymer of mainly being made up of ethylene repeating unit.It can contain the unit derived from other polymerisable monomer of trace, and still, based on all repeating units in the described low-molecular-weight ethylenic homopolymer component, it should contain in mole at least about 99.9% ethylene repeating unit.

Advantageously, based on the amount of described multimodal ethylene copolymer, multimodal ethylene copolymer (B-1) also comprise 40-60% by weight by ethene and have the high molecular weight copolymer (B-1-2) that the alpha-olefin of 4-10 carbon atom forms.High molecular weight copolymer component (B-1-2) has the weight-average molecular weight of 100000-700000g/mol, preferred 150000-300000g/mol.Preferably, based on the mole number of whole repeating units in the described high molecular weight copolymer, high molecular weight copolymer (B-1-2) also has the alpha-olefin comonomer composition with 4-10 carbon atom in mole 0.5-10%, preferred 1-5%.Preferably, high molecular weight ethylene copolymer component (B-1-2) is the multipolymer that ethene and one or more alpha-olefins with 6-10 carbon atom form.

It is main by ethylene repeating unit and the ethene polymers formed derived from the repeating unit of the alpha-olefin with 4-10 carbon atom to it should be understood that term of the present invention " multipolymer that ethene and the alpha-olefin with 4-10 carbon atom form " is used in reference to.It can also contain the unit derived from other polymerisable monomer of trace, but based on all repeating units in the described high molecular weight ethylene copolymer component, it should contain in mole at least about 99.9% above-mentioned repeating unit.

Except that above-mentioned two kinds of components, described multimodal ethylene copolymer can contain up to other polymeric constituent of 20% by weight.The amount of other polymeric constituent like this and performance can freely be selected, as long as the character of described multimodal ethylene copolymer and above-mentioned two kinds of components as mentioned above.

Polymerization process

Described multimodal ethylene copolymer can be with the polymerization process preparation of any appropriate in the prior art.Preferably, described multimodal ethylene copolymer prepares with continuous polymerization method, comprises at least two polymeric areas of operating under different condition, to make described multimodal multipolymer.Described polymeric area can be operated under slurry, solution or gas phase condition or their assembled state.Wherein, the method that is fit to is disclosed among WO-A-92/12182 and the WO-A-96/18662.

Catalyzer

In the presence of olefin polymerization catalysis, carry out polymerization.Catalyzer can be any catalyzer that can prepare whole components of described multimodal ethylene copolymer.Wherein, appropriate catalyst has based on transition metal, for example Ziegler-Natta catalyst of titanium, zirconium and/or vanadium or metallocene catalyst or late transition metal catalyst, and their mixture.Especially Ziegler-Natta catalyst and metallocene catalyst are useful, because they can be with the polymkeric substance of produced in high yields wide molecular weight scope.

Preferably, suitable Ziegler-Natta catalyst contains magnesium compound, aluminum compound and the titanium compound that supports on granular carrier.

Described granular carrier can be an inorganic oxide carrier, for example silicon oxide, aluminum oxide, titanium oxide, silica-alumina and silicon oxide-titanium oxide.Preferably, described carrier is a silicon oxide.

The average particle size particle size of described silica support generally can be 10-100 μ m.But, verified, if described carrier has the median size of 15-30 μ m, preferred 18-25 μ m, can obtain peculiar advantage.Selectively, described carrier can have the average particle size particle size of 30-80 μ m, preferred 30-50 μ m.The suitable carriers examples of material for example Ineos Silicas (preceding crossfield) company's production and selling ES747JR and by the SP9-491 of Grace company production and selling.

Described magnesium compound is the reaction product of dialkyl magnesium and alcohol.Alcohol is the aliphatic monobasic alcohol of linearity or branching.Preferably, described alcohol has 6-16 carbon atom.Especially preferred branched alcohol, an example of preferred alcohols is 2-ethyl-1-hexanol.Dialkyl magnesium can be magnesium and two identical or different alkyl linked any compounds.An example of preferred dialkyl magnesium is butyl-octyl group magnesium.

Described aluminum compound is chloride aluminum alkyls.Especially preferred compound is dichloro aluminum alkyls and sesquialter chlorine aluminum alkyls.

Described titanium compound is halogen-containing titanium compound, preferred chloride titanium compound.Especially preferred titanium compound is a titanium tetrachloride.

Described catalyzer can be by making the preparation of carrier and above-claimed cpd Continuous Contact, described in EP-A-688794 or WO-A-99/51646.Selectively, it also can be by preparing solution by described component earlier, and the method that this solution is contacted with carrier prepares then, described in WO-A-01/55230.

Especially preferably, the suitable Ziegler-Natta catalyst of another combination contains titanium compound and halogenated magnesium compound, does not contain inert support.Therefore, described catalyzer contains the titanium compound on magnesium dihalide, for example magnesium dichloride.This catalyzer for example is disclosed among the WO-A-2005/118655 and EP-A-810235.

Described Ziegler-Natta catalyst uses with activator.Suitable activator is an alkyl metal cpd, especially alkylaluminium cpd.These compounds comprise alkyl aluminum halide, for example ethyl aluminum dichloride, aluminium diethyl monochloride, sesquialter chloroethyl aluminium, a Chlorodimethyl aluminium etc.They also comprise trialkyl aluminium compound, for example trimethyl aluminium, triethyl aluminum, triisobutyl aluminium, three hexyl aluminium and tri-n-octylaluminiums.They also comprise the aluminum alkyls oxide compound, for example methylaluminoxane, six isobutyl aluminium alkoxides and four isobutyl aluminium alkoxides.In addition, also can use other alkylaluminium cpd, for example isopentene group aluminium.Especially preferred activator is a trialkylaluminium, wherein especially preferably uses triethyl aluminum, trimethyl aluminium and triisobutyl aluminium.

The usage quantity of described activator depends on concrete catalyzer and activator.Usually, the usage quantity of triethyl aluminum is the mol ratio that makes aluminium and transition metal, and for example Al/Ti is 1-1000, preferred 3-100 and especially be preferably the about 30mol/mol of about 5-.

As mentioned above, metallocene catalyst also can be used to prepare described multimodal ethylene copolymer.Suitable metallocene catalyst is well known in the prior art, wherein, be documented among WO-A-95/12622, WO-A-96/32423, WO-A-97/28170, WO-A-98/32776, WO-A-99/61489, WO-A-03/010208, WO-A-03/051934, WO-A-03/051514, WO-A-2004/085499, EP-A-1752462 and the EP-A-1739103.

Polymerization

The general operation temperature for preparing the polymeric area of described low-molecular-weight ethylenic homopolymer is 20-150 ℃, preferred 50-110 ℃, and more preferably 60-100 ℃.Polymerization can be carried out under slurry, gas phase or solution state.

Can catalyzer be moved into polymeric area by the known any way of prior art.Therefore, can be suspended in catalyzer in the thinner and keep the homogeneous phase slurry state.Especially preferredly be, use viscosity as the oil of 20-1500mPa.s as thinner, as disclosed among the WO-A-2006/063771.Also can with catalyzer and oil and the viscous mixt of fat mix and with gained mashed prod adding polymeric area.In addition, can make catalyst sedimentation and the catalyzer mud that obtains of part introduced polymeric area in disclosed mode among the EP-A-428054 for example.Before the polymeric area prepolymerization district can be arranged, in the case, the mixture that obtains from the prepolymerization district directly enters polymeric area.

Ethene, optional inert diluent and optional hydrogen and/or comonomer are also added described polymeric area.In first polymeric area, make described low-molecular-weight ethylenic homopolymer component, in second polymeric area, make described high molecular weight ethylene copolymer.Described first polymeric area can link to each other with second polymeric area in random order, that is, first polymeric area can be prior to second polymeric area, or second polymeric area can be prior to first polymeric area, or alternatively, polymeric area can be in parallel.But preferably, polymeric area is operated with series system.

As mentioned above, in first polymeric area, make described low molecular mass homopolymers.Ethene, hydrogen and optional inert diluent are added first polymeric area.Comonomer does not add first polymeric area.In first polymeric area, be aggregated in 50-150 ℃, preferred 80-110 ℃ and especially carry out under 90-105 ℃ the temperature.The pressure of first polymeric area is 1-300bar, preferred 5-100bar.

The polymerization of described first polymeric area can be carried out under slurry state.Then, polymer beads and pulverizing that polymerization is formed and the catalyzer that is scattered in the polymer beads are suspended in the liquid hydrocarbon.Reactant stirs slurry so that can change particle into by liquid.

Polymerization is usually at inert diluent, typically carry out in hydrocarbon diluent, and described hydrocarbon diluent is methane, ethane, propane, normal butane, Trimethylmethane, pentane, hexane, heptane, octane etc. for example, or their mixture.Thinner preferably has the low boiling hydrocarbon of 1-4 carbon atom or the mixture of such hydrocarbon.Especially preferred thinner is a propane, may contain a small amount of methane, ethane and/or butane.

It is about 50% that ethylene content in the liquid phase of slurry can be 2-in mole, and preferably about 3-is about 20%, especially about 5-about 15%.Benefit with high ethylene concentration is that the productive rate of catalyzer has improved, but shortcoming is to have that more ethene needs to reclaim when lower than ethylene concentration.

Slurry polymerization can carry out in any reactor that becomes known for slurry polymerization.Such reactor comprises continuous stirred tank reactor and loop reactor.Especially preferably in loop reactor, carry out.In this reactor, by using recycle pump, slurry circulates at a high speed along closed conduct.Loop reactor is commonly known in the art, and for example, US-A-4582816, US-A-3405109, US-A-3324093, EP-A-479186 and US-A-5391654 have provided example.

Carrying out described slurry polymerization in the critical temperature of liquid mixture with more than the pressure is favourable sometimes.This operation is documented among the US-A-5391654.

According to the amount of the melt flow rate (MFR) adjustment hydrogen of expecting, the amount of hydrogen also depends on the concrete catalyzer of use.For many general Ziegler-Natta catalysts, the mol ratio of hydrogen and ethene is 100-1500mol/kmol, preferred 200-1200mol/kmol, especially 300-1000mol/kmol.

Polymerization in described first polymeric area also can be carried out under gas phase state.A preferred embodiment of gas-phase polymerization reactor is a fluidized-bed reactor.Wherein the polymer beads of polymerization formation is suspended in the flowing gas that makes progress.Described gas is introduced reactor bottom.Upwards mobile gas is by fluidized-bed, and wherein portion gas reacts in the presence of catalyzer, and unreacted gas is discharged from reactor head.Then with gas compression, cooling, to remove heat of polymerization.In order to improve cooling power, wish sometimes recycle gas is cooled to portion gas agglomerative temperature.After the cooling, recycle gas is introduced described reactor bottom again.Fluidized-bed reactor for example is disclosed among US-A-4994534, US-A-4588790, EP-A-699213, EP-A-628343, FI-A-921632, FI-A-935856, US-A-4877587, FI-A-933073 and the EP-A-75049.

In the vapour phase polymerization of using Ziegler-Natta catalyst, it is 500-10000mol/kmol, the preferred 1000-5000mol/kmol molecular weight with the low-molecular-weight ethylenic homopolymer component of acquisition expectation that the amounts of hydrogen of interpolation makes the ratio of hydrogen and ethene usually.

The described high molecular weight copolymer that forms by the alpha-olefin of an ethene and at least a 6-10 of a having carbon atom of preparation in second polymeric area.Ethene, the alpha-olefin with 6-10 carbon atom, hydrogen and optional inert diluent are added second polymeric area.In second polymeric area be aggregated in 50-100 ℃, preferred 60-100 ℃, especially carry out under 70-95 ℃ the temperature.The pressure of second polymeric area is 1-300bar, preferred 5-100bar.

Polymerization in second polymeric area can be carried out under slurry state.Then, polymerization can be carried out along the circuit of first polymeric area as mentioned above.

According to the amount of the melt flow rate (MFR) adjustment hydrogen of expecting, the amount of hydrogen also depends on the concrete catalyzer of use.For many general Ziegler-Natta catalysts, the mol ratio of hydrogen and ethene is 0-50mol/kmol, preferred 10-35mol/kmol.

In addition, adjust the amount of alpha-olefin to obtain target density with 6-10 carbon atom.The ratio of alpha-olefin and ethene is 100-500mol/kmol normally, preferred 150-350mol/kmol.

Polymerization in second polymeric area also can be carried out under gas phase state.In the vapour phase polymerization of using Ziegler-Natta catalyst, it is 5-500mol/kmol, the preferred 30-150mol/kmol molecular weight with the high molecular weight ethylene copolymer component (B-1-2) of acquisition expectation that the amounts of hydrogen of interpolation makes the ratio of hydrogen and ethene usually.Adjustment has the amount of alpha-olefin of 6-10 carbon atom to obtain target density.The ratio of alpha-olefin and ethene is 10-300mol/kmol normally, preferred 30-200mol/kmol.

Coating composition

Coating composition (B-2) comprises multimodal ethylene copolymer (B-1) and final additive and other polymkeric substance.Coating composition (B-2) comprises by weight preferred 80-100%, the more preferably multimodal ethylene copolymer of 85-100%, especially 90-99% (B-1).

Except that the bimodal ethylene multipolymer, coating composition (B-2) can comprise the prior art known additives.Wherein, these additives are antioxidant, processing stabilizers, UV stablizer, pigment and acid-acceptor.

Suitable antioxidant and stablizer are, for example, 2, [methylene radical-3-(3 ' for 6-two-Butylated Hydroxytoluene, four, 5-di-t-butyl-4 '-hydroxyphenyl) propionic ester] methane, octadecyl-3-3 (3 ', 5 '-di-t-butyl-4 '-hydroxyphenyl) propionic ester, Tyox B, the two octadecyl esters of thio-2 acid, three nonyl phenyl phosphate ester, two octadecyl pentaerythritol diphosphites and four (2, the 4-di-tert-butyl-phenyl)-4,4 '-biphenyl, two phosphinates.

Some hindered phenols are sold with trade(brand)name Irganox 1076 and Irganox 1010.Also can obtain the blend of commercial antioxidant and processing stabilizers, for example the Irganox B225 that sells by vapour Ba-Jia Ji (Ciba-Geigy) company.

Suitable acid-acceptor is that for example, Metallic stearates is as calcium stearate and Zinic stearas.They use with amount well known in the art, generally are 500ppm-10000ppm, preferred 500-5000ppm.

Carbon black is a universal pigment, also can be used as the UV screener.Usually, the sooty usage quantity is 0.5-5% by weight, preferred 1.5-3.0%.Preferably, carbon black adds as masterbatch with specified quantitative, carries out premix with polymkeric substance, preferred high density polyethylene(HDPE) (HDPE).Wherein, suitable masterbatch has HD4394 that is sold by Cabot (Cabot) company and the PPM1805 that is sold by Polyplast Muller company.Titanium oxide also can be used as the UV screener.

In addition, coating composition (B-2) can also contain other polymkeric substance, for example is used for the carrier polymer of additive masterbatch.The content of this polymkeric substance and performance can freely be selected in above-mentioned discussion scope, as long as the performance of coating composition is not subjected to negative impact.

Also can in coating composition (B-2), add the sticky polymers of appropriate amount to improve the binding property between pipe and the coating.With this method, the amount that is used for the polymkeric substance of tack coat can reduce, and in some cases, may can get rid of tack coat fully.

Preferably, coating composition (B-2) has the velocity ratio FRR of 2-10, preferred 2-6, especially 3-5 _5/2Preferably, have 15-40, the more preferably velocity ratio FRR of 20-35 _21/5And/or the shear shinning index SHI of 25-100 _2.7/210

Coating composition (B-2) preferably has high environmental stress crack resistance.Therefore, measure by CTL (constant stretch load) under 60 ℃ and 5MPa, coating composition (B-2) has preferred 10h at least, the more preferably anti-stress cracking of 15h at least.This is noticeable, because known anti-environmental stress can significantly reduce along with the increase of density.Yet although described multimodal ethylene copolymer has high-density, composition of the present invention still has acceptable CTL.

Coating composition (B-2) has the highest by 25 preferred, more preferably the highest 20 wear index.

Coating composition (B-2) has excellent high-temperature behavior.This shows as high vicat softening temperature, and preferably at least 117 ℃, more preferably at least 119 ℃ and especially preferably at least 120 ℃.

Coating composition (B-2) has preferred 0.05-5g/10min, the more preferably melting index MFR of 0.1-1.2g/10min and especially preferred 0.2-1.0g/10min ₂It also has preferred 0.5-10g/10min, the more preferably melting index MFR of 1.0-5.0g/10min ₅

Coating composition (B-2) has preferred 800MPa at least, more preferably 850MPa and the especially preferred tensile modulus of 900MPa at least at least.

Coating composition has preferred at least 59.0, more preferably at least 60.0 high shore hardness.

Especially preferably, coating composition (B-2) combines high vicat softening temperature and high CTL value, and its vicat softening temperature is at least 10 hours at least 117 ℃ with the CTL value, more preferably, vicat softening temperature is at least 119 ℃, and especially preferably at least 120 ℃ and CTL value are at least 15 hours.Especially, these character are combined in the coating composition, and described coating composition has 0.05-5g/10min, preferred 0.1-1.2g/10min and the more preferably melting index MFR of 0.2-1.0g/10min ₂

Selectively, coating composition (B-2) preferred combination high vicat softening temperature, high tensile modulus and high CTL value, its vicat softening temperature is at least 117 ℃, tensile modulus is for 800MPa and CTL value are at least 10 hours at least, more preferably, vicat softening temperature at least 119 ℃ and especially preferably at least 120 ℃ and tensile modulus for 850MPa and CTL value are at least 15 hours at least.

Coating

Described coated pipe has the coating (B) that comprises coating composition (B-2).Based on the gross weight of coating (B), coating (B) comprises at least 75%, preferred at least 80% and more preferably at least 90% coating composition (B-2) by weight.Especially preferably, coating (B) is made up of coating composition (B-2).

Pipe coating and coated pipe

As be known in the art, preferably before carrying out coating, tube-surface is suitably handled.Usually, the rusty stain on access tube surface, dirt, flaw, fracture and metal defect.Need remove all excess stocks from tube-surface suitably sticks on the pipe to guarantee coating.Suitable purging method comprises that sky G﹠W high pressure cleaning, sandblast or shot peening and brusher remove.Sometimes also use pickling and chromic salt pre-treatment.

Generally, by induction heating pipe is heated to up to about 200 ℃.Can adjust temperature according to the material of linear velocity and preservative coat (C) use.When using epoxy Teknos AR8434, preferably steel pipe is heated to 190 ℃.In coating procedure, temperature slightly reduces.

If use epoxy powder (at 23 ℃), generally to spray by the epoxy rifle, rotational line speed is about 8m/min.The thickness of epoxy and other coated material uses the requirement of regulation to set according to final.The general thickness of epoxy layer is 70-200 μ m, for example 135 μ m.

The material that can be used for preservative coat (C) is, for example, and Resins, epoxy and silicoorganic compound.The example of suitable Resins, epoxy is phenol-type epoxy resin and amine type Resins, epoxy.Wherein, these Resins, epoxy are sold with trade(brand)name AR8434 (Teknos company), Scotchkote 226N (3M company) and PE50-7191 (BASF (BASF) company).Suitable silicoorganic compound are open in EP-A-1859926.

Can extrude tack coat (D) and coating (B) by for example two single screw extrusion machines.Described two single screw extrusion machines have for example 30-100mm, as diameter and the 15-50L/D of 60mm, as the length of 30L/D.The temperature in the several districts of general control, PE tack coat (D) and coating (B) are 190-300 ℃ through the temperature behind the extrusion die, for example are respectively 225 ℃ and 250 ℃.The extrusion die width is 50-300mm, is respectively 110mm and 240mm for tack coat (D) and coating (B) for example.General by the silicone resin pressure roll with tack coat (D) and coating (B) tightly roll-in on pipe.The thickness of tack coat (D) generally is 200-400 μ m, for example 290 μ m.The thickness of coating (B) generally is 1-5mm, preferred 2-4mm, for example 3.2mm.

The material that is suitable for tack coat (D) for example is acid or acid anhydride-grafted olefin polymer, as polyethylene or polypropylene.Wherein, suitable polymers is fumaric acid modified poly ethylene, fumaric acid anhydride modified poly ethylene, toxilic acid modified poly ethylene, maleic anhydride modified polyethylene, fumaric acid modified polypropene, fumaric acid anhydride modified polypropene, toxilic acid modified polypropene, maleic anhydride modified polypropylene.The example of especially preferred adhered plastics can be referring to EP-A-1316598.

After the coating, for example by providing current that coated pipe is cooled off on the coated pipe surface.

Coated pipe of the present invention has improved mechanical property, for example very high vicat softening temperature and acceptable anti-stress cracking.In addition, coating composition (B-2) has high rigidity and acceptable anti-stress cracking.And described coated pipe has high rigidity.In addition, the multimodal ethylene copolymer (B-1) that is included in the coating composition (B-2) has wide molecular weight distribution, makes it possible to make described coated pipe with high yield and good production economy.

[embodiment]

Method

CTL

Measure CTL by adopting the following method similar to ISO 6252:1992.

Under 180 ℃ and 10MPa pressure, be that 125-130mm and terminal width are that the plate of 21 ± 0.5mm prepares sample by applying pressure to length overall.Then plate is ground into the appropriate size in the anchor clamps of both sides, the width between centers of two clampers is that 90mm and aperture are 10mm on the both sides.The parallel length of the centre portions of this plate is 30 ± 0.5mm, and width is 9 ± 0.5mm, and thickness is 6 ± 0.5mm.

Then, with the blade that places slotting machine (PENT-NOTCHER, Norman Brown engineering) sample is cut out the dark front otch of 2.5mm, grooving speed is 0.2mm/min.On two other side, cut out should with the side channel of the coplanar 0.8mm of otch.After making otch, sample was placed under the condition of 23 ± 1 ℃ and 50% relative humidity at least 48 hours.Then sample being packed into, it contains in the experiment container of the living solution (deionized water solution of 10% IGEPAL CO-730, chemical substance: 2-(4-nonyl-phenoxy group) ethanol) that remains on 60 ℃.To load on sample corresponding to the static load of the initial stress of about 5MPa, and close timing register in fracture moment.The mean value of record at least twice measurement.

Otch on sample and the sample is seen Fig. 1, wherein:

A: sample length overall 125-130mm

B: the width between centers 90mm of two clampers

C: the terminal width 21 ± 0.5mm of sample

D: aperture 10mm

E: side channel 0.8mm

F: thickness of slab 6 ± 0.2mm

G: the width 9 ± 0.5mm of narrow parallel portion

H: main otch 2.5 ± 0.02mm

The length of sample crevice is 30 ± 0.5mm.

GPC

Measure weight-average molecular weight Mw and molecular weight distribution (MWD=Mw/Mn, wherein Mn is a number-average molecular weight, Mw is a weight-average molecular weight) according to method shown in ISO 16014-4:2003 and the ASTM D 6474-99.The equipment Waters GPCV2000 that RI-detector and in-line viscometer be housed with available from the post 2 * GMHXL-HT of eastern Cao's biotechnology company (Tosoh Bioscience) and 1 * G7000H and temperature be 140 ℃ and constant flow rate be 1mL/min as 1 of solvent, 2,4-trichlorobenzene (TCB, with 2 of 250mg/L, 6-di-t-butyl-4-sylvan is stable) use together.Inject 209.5 μ L sample solutions during each the analysis.Proofread and correct colonnade (column set) with universal calibration method (according to ISO 16014-2:2003) with the polystyrene in the 1kg/mol-12000kg/mol scope (PS) standard specimen of 15 narrow MWD.Mark-Houwink (Mark Houwink) constant is used for polystyrene and polyethylene (K:19 * 10 that are used for PS ^-3ML/g, a:0.655 is used for K:39 * 10 of PE ^-3ML/g, a:0.725).By dissolving 0.5-3.5mg polymkeric substance in the TCB (identical) of 4mL (140 ℃) stabilization with mobile phase and before sample being sent in the GPC instrument 160 ℃ of following continuous shakings and be incubated maximum 3 hours and prepare all samples.

Melting index, melt flow rate (MFR), velocity ratio (MI, MFR, MRR):

Melting index (MI) or melt flow rate (MFR) (MFR)

Represent according to ISO 1133 mensuration melt flow rate (MFR)s (MFR) and with g/10min.MFR is the indication of polymer malt viscosity.At 190 ℃ of MFR that measure PE.The load of using when measuring melt flow rate (MFR) generally represents with the form of subscripts, for example, and MFR ₂Under 2.16kg load, measure MFR ₅Under 5kg load, measure MFR ₂₁Under 21.6kg load, measure.

Velocity ratio (FRR)

Amount FRR (velocity ratio) is characterizing molecular weight distribution, shows the velocity ratio under the different loads.Therefore, FRR _21/2Expression MFR ₂₁/ MFR ₂Value.

The width of cloth (neck-in) contracts

The width of cloth that contracts is used to represent that the film through after the 110mm extrusion die is wide, represents with mm.In this series of tests, the record width of cloth that contracts under the largest circumference speed of the pipe that can realize (manage) under the constant condition of fused film width.Under the winding speed of 20RPM, measure the width of cloth that contracts.

Stripping strength

Polymkeric substance to the adhesivity of steel according to DIN 30670, by Instron (Instron) 1122 peel strength test device to test.Downcut the wide batten of 3cm from coating.The other end of batten is fixed on the stretching device, and stripping strength is measured from the process that steel are peeled off with the draw speed of 10mm/min at batten.The result represents with N/cm.Measure stripping strength by the coating that under the screw speed of 50RPM, makes.

Pipe coating

The cleaning diameter is that the steel pipe of 114mm is to remove excess stock from its surface.By induction heating described pipe is heated to 190 ℃ then.Epoxy powder (Teknos AR8434) is sprayed on tube-surface with the rotational line speed of 9m/min, so that the thickness of epoxy layer is 135 μ m.Then, use L/D than be 24, diameter is Ba Mage (Barmag) single screw extrusion machine of 45mm, will be according to the viscous plastic of 2 preparations of the composition among the EP1316598 A1, i.e. maleic anhydride grafted polyethylene tackiness agent, being extruded on the pipe, is 225 ℃ through the melt temperature after the extrusion die.The extrusion die width is 110mm.Simultaneously, be 45mm, L/D than being 30 by diameter Crouse's agate phenanthrene(Krauss-Maffei) forcing machine is extruded into the composition of embodiment 1 on the described tack coat.The extrusion die width is 240mm, is 250 ℃ through the melt temperature after the extrusion die.With 25,50 and the extruder screw rotating speed of 100RPM prepare described coating.Under the screw speed of 25RPM, take five kinds of different winding speeds, promptly 9,15,20,25 and 30RPM.Under the screw speed of 100RPM, measure peak performance.

Rheological

Adopt Anton Paar Phisica MCR 300 rheometers, use diameter as the plate of 25mm and gap as the plate board clamp (geometry) of 1.2mm under nitrogen atmosphere, 190 ℃, measure the rheological parameters of compression moulded samples, for example shear shinning index SHI and viscosity.In strain (strain) linear viscosity scope, carry out oscillatory shear test (ISO6721-1) under the 0.05-300rad/s frequency.Carry out according to 5 test point of per 10 octaves.

Record the value of storage modulus as frequency (ω) function (G '), loss modulus (G "), complex modulus (G*) and complex viscosity (η *).η ₁₀₀It is the abbreviation of the complex viscosity under the 100rad/s frequency.

According to Heino (" Rheological characterization of polyethylenefractions (rheological properties of polyethylene fragment) ", Heino, E.L., Lehtinen, A., Tanner J.,

J., Neste Oy, Volvo (Porvoo), Finland, Theor.Appl., Rheol., Proc.Int.Congr.Rheol, 11th (1992), 1,360-362, and " The influence of molecular structure on some rheologicalproperties of polyethylene (molecular structure is to the influence of more poly rheological properties) ", Heino, E.L., Borealis A/S (Borealis Oy), Volvo, Finland, Annual Transactions of the Nordic Rheology Society, 1995.) calculate relevant and do not depend on M with MWD _wShear shinning index (SHI).

Obtain the SHI value by the ratio that calculates the complex viscosity under the given modulus of complex number value and calculate two viscosity.For example, adopt the modulus of complex number value of 1kPa and 100kPa, under the constant modulus of complex number value of 1kPa and 100kPa, obtain η * (1kPa) and η * (100kPa) respectively.With the ratio of two viscosities il * (1kPa) and η * (100kPa), promptly η (1)/η (100) determines shear shinning index SHI then _1/100

It is always unfeasible directly to measure complex viscosity under low frequency value.Described value can obtain by following manner extrapolation: test being low to moderate under the frequency of 0.126rad/s, in logarithmic coordinates, frequency is mapped with complex viscosity, draw by best-fit line, and read viscosity number from described line corresponding to five points of lowest frequency value.

Shore hardness

Measure Shao Shi D hardness according to ISO 868-2003.At diameter is that 35mm, thickness are to measure on the disk of 4mm, and described disk is that the holoplast punching press of 4mm obtains from thickness.According to ISO1872-2,, make holoplast molded with the rate of cooling of 15 ℃/min at 180 ℃.At last, model was placed 2 days under the condition of 23 ℃ and 50% relative humidity at least.

Each sample carries out 5 times and measures.Select measurement point so that itself and web have the distance of 10mm at least and nearest previous measurement point 6mm at least.

During measurement, (quality is 5kg) is pressed into specimen with a specific pressure head (D type hardness tester meter) under given conditions.Behind the 15s, remove described quality, measure the degree of depth of passing.

Wear index

According to ASTM D 4060,, model determines wear index by being carried out the Taber wear test.

Sample is the holoplast of 100 thick * 100mm of 2mm, the hole that it is 6.3mm that the center of described holoplast has a diameter.The insulation at least 24 hours under 23 ℃ and 50% relative humidity of described sample.Use the CS-17 emery wheel to carry out this test.By being put in sample in the device and making emery wheel rotation 50 circles adjust emery wheel.Conscientiously clean sample then and weigh, afterwards, sample is placed on begins test in the test set.The following calculating of wear index (I):

I = \frac{(A - B) \cdot 1000}{C}

Wherein, the weight of sample before the A=abrasion, the weight of B=abrasion back sample, the abrasive number of turns of C=.

When test begins at every turn, enclose back adjustment emery wheels with abrasion 500.

Density

Measure the density of polymkeric substance according to 1183-2/1872-2B.

Tensile strength

Measure tensile strength properties according to ISO 527-2.Use is according to the 1A type compression moulded samples of ISO 1872-2B preparation.

Yield strain

Measure yield strain (representing) according to ISO 527-2 with %.This measurement is to carry out under the condition of 50mm/min at 23 ℃, extension speed.

Yielding stress

Measure yielding stress (representing) according to ISO 527-2 with MPa.This measurement is to carry out under the condition of 50mm/min at 23 ℃, extension speed.

Tensile modulus

Measure tensile modulus (representing) according to ISO 527-2 with MPa.This measurement is to carry out under the condition of 1mm/min at 23 ℃, extension speed.

Tension fracture

Measure tension fracture (representing) according to ISO 527-2 with MPa.This measurement is to carry out under the condition of 50mm/min at 23 ℃, extension speed.

DSC

Measure the fusing point (T of 3 ± 0.5mg sample with Mettler TA820 differential scanning calorimeter (DSC) _m) and Tc (T _Cr).With the cooling of 10 ℃/min with add heat scan and obtain crystallization and melting curve between-10 to 200 ℃.Fusing point and Tc are considered to endotherm(ic)peak and exothermic peak respectively.By with the Heat of fusion of perfect crystalline polyethylene, i.e. 290J/g, degree of crystallinity is calculated in contrast.

Co-monomer content

Adopt the content of comonomer in the 13C-NMR assay determination sample.In the NMR of 10ml pipe, by about 0.100g polymer dissolution is prepared sample in the 2.5ml solvent.Solvent be 90/10 1,2, the mixture of 4-trichlorobenzene and benzene-d6.By 150 ℃ of down heating NMR pipe and contents thereof in well heater, make sample dissolution and homogenize.

The proton decoupling carbon-13 monopulse NMR spectrum that has NOE by Joel EXC 400MHz NMR spectrophotometer.The acquisition parameter that is used for this experiment comprises that flip angle 45 degree, vacation sweep number of times 4, several 3000 (3000transients) of sampling transient state, sampling time 1.6s, spectrum width 20kHz, 125 ℃ of temperature, WALTZ decoupling and relaxation delay 6.0s.Used processing parameter comprises that zero padding to the 32k data point with cut toe, uses the power window function of 1.0Hz with interior bootstrap broadening, and automatic zero level afterwards and one-level phase correction and baseline correction automatically.

Works (JMS-Rev.Macromol.Chem.Phys., C29 (2﹠amp according to JC.Randall; 3), 201-317 (1989)) the middle mode of putting down in writing, the integration that use is obtained by the spectrogram after handling recently calculates the content of comonomer, wherein:

E＝(\αB+\αH+\βB+\βH+\γB+\γH+\δ ⁺⁺)/2

B＝(methine?B+2B+1B)/3

H＝(methine?H+4H+3H+2H)/4

Wherein, methine (methyne) is the CH branch point, and α, β, γ are the carbon potentials adjacent with CH, that is, and and CH, α, β, γ, δ.δ ⁺⁺Be main body CH ₂The position, 1,2,3 and 4 representative is along each carbon potential with side chain of methyl, and described methyl is designated as 1.

CE＝100％*E/(E+B+H)

CB＝100％*B/(E+B+H)

CH＝100％*H/(E+B+H)

Embodiment 1

Volume is 50dm ³Loop reactor non-stop run under 60 ℃ and 62bar pressure.In described reactor, introduce propane thinner, the ethene of 2kg/h and the hydrogen of 34g/h of 40kg/h.In addition, in reactor, add solid polymerization catalyst component (selling with trade(brand)name Lynx 200) and the triethyl aluminum catalyst of 6.1g/h, so that the ratio of aluminium and titanium is 30mol/mol by BASF AG.Polymer production rate is about 1.8kg/h.

With slurry from 50dm ³Loop reactor in to be continuously removed and to move into another volume be 500dm ³, in the loop reactor of under the pressure of 95 ℃ and 60bar, working.In reactor, introduce other propane thinner, ethene and hydrogen.The content of ethene is 3.4mol% in the liquid phase, and polymer production rate is about 33kg/h.Actual conditions and data are referring to table 1.

By sedimentation leg (settling legs) slurry is moved into the flasher of working under 50 ℃ of temperature and 3bar pressure from loop reactor, in this flasher, remove hydrogen and most of hydrocarbon in the polymkeric substance.Polymkeric substance directly enters the gas fluidized bed reactor of working under the pressure of 85 ℃ temperature and 20bar.In ethene, 1-hexene co-monomer, hydrogen and the nitrogen adding reactor with other as rare gas element.Ethylene content in the fluidizing agent is 16mol%.Actual conditions and data are referring to table 1.

The polymer powder drying that obtains is taken off hydrocarbon, and mix with the calcium stearate of Irganox B225, the 1000ppm of 3000ppm and 2.4% carbon black based on the amount of final composition.Use CIM90P twin screw extruder (making) that mixture is extruded then and form particle by Japanese Steel Works company.The character of gained mixture sees Table 2.

Resulting composition is used for coating steel pipes, and that puts down in writing in the described method under the title in the book as described above " pipe coating " is such.Related data sees Table 2.

Embodiment 2-5 and reference example 6R and 7R

Except using condition as shown in table 1, repeat the process of embodiment 1.

The data of gained mixture and coated pipe see Table 2.

Table 1: polymerizing condition

Embodiment	1	2	3	4	5	6R	7R
								H in the loop reactor ₂/C ₂，mol/kmol	558	752	745	745	757	722	536
MFR ₂, in the loop reactor, dg/min	400	800	815	815	575	770	280

M _w, in the loop reactor, g/mol	31000	24000		22000	30000	25000	32000
								H ₂/C ₂, in the Gas-phase reactor, mol/kmol	104	103	98	98	89	53	73
C ₆/C ₂, in the Gas-phase reactor, mol/kmol	78	71	70	70	78	133	2361)
								Share, loop reactor/Gas-phase reactor	45/55	51/49	51/49	51/49	51/49	49/51	45/55
MFR ₂(matrix resin), g/10min	0.54	0.52	0.58	0.61	0.54	0.61	0.57
								MFR ₅(matrix resin), g/10min	2.2	2.3	2.5	2.6	2.4	2.7	2.2
Density (matrix resin), kg/m ³	946.3	949.7	950.0	949.9	948.4	941.1	940.3
								The forcing machine productive rate, kg/h	217	203	202	201	194	213	200
SEI，kWh/ton	168	169	174	152	148	146	166
								Fusing point, ℃	222	226	226	222	223	217	230

Annotate: ¹⁾1-butylene is as comonomer, C ₄/ C ₂Ratio

Table 2:

Embodiment	1	2	3	4	5	6R	7R
								MFR ₂，g/10min	0.56	0.53	0.61	0.59	0.53	0.65	0.58
MFR ₅，g/10min	2.3	2.3	2.7	2.5	2.4	2.8	2.3
								MFR ₂₁，g/10min	49	57	71	68	68	ND	ND

Density, kg/m ³	958.3	962.0	961.9	960.4	963.2	952.0	951.8
								η0.05，Pa.s	21869	24412	22569	22721	25165	22623	21006
η ₃₀₀，Pa.s	599	543	524	519	525	495	616
								SHI(2.7/210)	37.2	56.8	56.6	58.4	65.4	69.3	33.3
The dimension card, ℃	122.4	122.8	122.5	122.3	122.1	116.1	116.7
								Tensile modulus, MPa	901	1004	1008	1019	933	771	731
Tensile stress at yield, MPa	22.5	24.3	24.3	24.3	23.5	19.5	19.5
								Shore hardness	60.0	61.7	61.0	61.2	60.7	58.2	58.3
CTL，h	30	20	16	16	22	118	52
								Wear index	18.8	18.2	19	19.4	24.7	25.0	18.3
Tc, ℃	117.2	117.2	117.4	117.0	117.5	116.4	116.3
								Degree of crystallinity, %	62.5	62	65.5	66.5	65.5	56	58
M _w，g/mol	138000	134000	ND	125000	140000	127000	115000
								M _n，g/mol	4570	4160	ND	3600	3990	4280	5000
M _w/M _n	30.2	32.3	ND	34.7	35.1	29.6	22.9
								Stripping strength under 23 ℃	550	279	322	411	393	385	556
Stripping strength under 80 ℃	195	193	161	185	168	208	232
								The width of cloth that contracts under the 20rpm, mm	80	80	83	83	85	84	78
Productive rate, kg/h	76.3	78.9	83.8	83.1	79.2	78.3	71.9

ND: undetermined

Claims

1. one kind comprises internal surface, the pipe of outer surface layer (A) and coating (B), described coating (B) covers described outer surface layer (A), wherein, coating (B) comprises coating composition (B-2), described coating composition comprises multimodal ethylene copolymer (B-1), the multipolymer of described multimodal ethylene copolymer for forming by ethene and one or more alpha-olefin comonomer with 4-10 carbon atom, wherein, the weight-average molecular weight of described multimodal ethylene copolymer (B-1) is 70000-250000g/mol, the melting index MFR that records under 190 ℃ and 2.16kg load according to ISO 1133 ₂Be 0.05g/10min-5g/10min, the melting index MFR that under 190 ℃ and 5kg load, records according to ISO 1133 ₅Be 0.5-10g/10min, density is 945kg/m ³-958kg/m ³

2. pipe according to claim 1 is characterized in that, the density of described multimodal ethylene copolymer (B-1) is 946-956kg/m ³, preferred 946-954kg/m ³

3. pipe according to claim 1 and 2 is characterized in that, the melting index MFR that described multimodal ethylene copolymer (B-1) records under 190 ℃ and 2.16kg load according to ISO 1133 ₂Be 0.1-1.2g/10min, preferred 0.2-1.0g/10min and the melting index MFR that under 190 ℃ and 5kg load, records according to ISO 1133 ₅Be 1.0-5.0g/10min.

4. according to the described pipe of aforementioned arbitrary claim, it is characterized in that the vicat softening temperature of described coating composition (B-2) is at least 117 ℃, more preferably at least 119 ℃, especially preferably at least 120 ℃.

5. pipe according to claim 1 and 2 is characterized in that, records under 60 ℃ and 5MPa by CTL (constant stretch load), and the anti-stress cracking of described coating composition (B-2) is at least 10 hours, preferably at least 15 hours.

6. according to the described pipe of aforementioned arbitrary claim, it is characterized in that described coating composition (B-2) is at least 59 according to the shore hardness of ISO 868-2003, preferably at least 60.

7. according to the described pipe of aforementioned arbitrary claim, it is characterized in that, record that the tensile modulus of described coating composition (B-2) is 800MPa at least, preferably 850MPa at least according to ISO 572-2.

8. according to the described pipe of aforementioned arbitrary claim, it is characterized in that described multimodal ethylene copolymer (B-1) comprising:

Weight based on described multimodal ethylene copolymer (B-1) is the low-molecular-weight ethylenic homopolymer component (B-1-1) of 40-60%, and the weight-average molecular weight of described low-molecular-weight ethylenic homopolymer component (B-1-1) is 5000g/mol-70000g/mol; With

Weight based on described multimodal ethylene copolymer (B-1) is the high molecular weight ethylene copolymer component (B-1-2) of 60-40%, described high molecular weight ethylene copolymer component (B-1-2) is the multipolymer that is formed by ethene and one or more alpha-olefin comonomer with 4-10 carbon atom, and its weight-average molecular weight is 100000g/mol-700000g/mol.

9. according to the described pipe of aforementioned arbitrary claim, it is characterized in that described multimodal ethylene copolymer (B-1) and described high molecular weight ethylene copolymer component (B-1-2) are the multipolymers that is formed by ethene and one or more alpha-olefin comonomer with 6-10 carbon atom.

10. according to the described pipe of aforementioned arbitrary claim, it is characterized in that described pipe is a metal tube.

11., it is characterized in that described outer surface layer (A) is covered by preservative coat (C) according to the described pipe of aforementioned arbitrary claim, described preservative coat is further covered by described coating (B).

12. pipe according to claim 11 is characterized in that, the bonded layer of described preservative coat (C) (D) covers, and described tack coat is further covered by described coating (B).

13., it is characterized in that the bonded layer of described outer surface layer (A) (D) covers according to any described pipe among the claim 1-10, described tack coat is further covered by described coating (B).

14., it is characterized in that based on the gross weight of described coating (B), described coating (B) comprises being the described coating composition (B-2) of 75-100%, preferred 80-100%, especially 90-100% by weight according to the described pipe of aforementioned arbitrary claim.

15., it is characterized in that based on the gross weight of described coating composition (B-2), described coating composition (B-2) comprises being the described multimodal ethylene copolymer (B-1) of 80-100%, preferred 90-99% by weight according to the described pipe of aforementioned arbitrary claim.

16., it is characterized in that the SHI of described coating composition (B-2) according to the described pipe of aforementioned arbitrary claim _2.7/210Be 25-100, wherein said SHI _2.7/210Be according to ISO 6721-1 by in the oscillatory shear test determination in strained linear viscosity scope under the 0.05-300rad/s frequency, be viscosity ratio η (2.7kPa)/η (210kPa).

17., it is characterized in that the ratio M of the weight-average molecular weight of described multimodal ethylene copolymer (B-1) and number-average molecular weight according to the described pipe of aforementioned arbitrary claim _w/ M _nBe 15-50, preferred 20-40, especially 25-40.

18. a method of making coated pipe may further comprise the steps:

The have outer surface layer pipe of (A) is provided;

The outer surface layer (A) that coating composition (B-2) is imposed on pipe is gone up to form coating (B), wherein said coating composition (B-2) comprises multimodal ethylene copolymer (B-1), described multimodal ethylene copolymer is the multipolymer that is formed by ethene and one or more alpha-olefin comonomer with 4-10 carbon atom, the weight-average molecular weight of wherein said multimodal ethylene copolymer (B-1) is 70000-250000g/mol, the melting index MFR that records under 190 ℃ and 2.16kg load according to ISO 1133 ₂Be 0.05g/10min-5g/10min, the melting index MFR that under 190 ℃ and 5kg load, records according to ISO 1133 ₅Be 0.5-10g/10min, density is 945kg/m ³-958kg/m ³

19. method according to claim 18 may further comprise the steps:

(i) at first polymerization stage, in the presence of polymerizing catalyst, hydrogen, ethene and optional inert diluent, polymerization low-molecular-weight ethylenic homopolymer component (B-1-1) is the Alathon of 5000g/mol-70000g/mol with the preparation weight-average molecular weight, and it constitutes the 40-60% of described multimodal ethylene copolymer (B-1) weight; With

(ii) at second polymerization stage, at polymerizing catalyst, ethene, carry out polymerization under the existence of the alpha-olefin comonomer of at least a 6-10 of a having carbon atom and hydrogen of choosing wantonly and/or inert diluent with preparation high molecular weight ethylene copolymer component (B-1-2), described high molecular weight ethylene copolymer component (B-1-2) is the multipolymer that is formed by ethene and one or more alpha-olefin comonomer with 6-10 carbon atom, weight-average molecular weight with 200000g/mol-700000g/mol, described high molecular weight ethylene copolymer component (B-1-2) constitute the 40-60% of described multimodal ethylene copolymer (B-1) weight; And wherein said first polymerization and second polymerization procedure carry out with the successive polymerization step, and any polymer product that makes in preceding step is present in subsequently the step, and the described first step and second step can be carried out with random order;

(iii) reclaim described multimodal ethylene copolymer (B-1);

(iv) obtain coating composition (B-2), it is the described multimodal ethylene copolymer (B-1) of 80-100%, preferred 85-100%, particularly 90-99% by weight that described coating composition (B-2) contains, optional additive and other optional polymkeric substance;

(v) described coating composition (B-2) being imposed on described tube outer surface layer (A) goes up to form described coating (B).

20. method according to claim 19 is characterized in that, described polymerization procedure (i) carries out in prior to described polymerization procedure polymerization stage (ii).

21. method according to claim 19 is characterized in that, described polymerization procedure (ii) carries out in prior to the polymerization stage of described polymerization procedure (i).

22. according to any described method among the claim 19-21, it is characterized in that, carry out polymerization in the presence of polymerizing catalyst, described polymerizing catalyst comprises that titaniferous, halogen and magnesium also randomly support the solids fraction on granular carrier, and aluminum alkyl catalyst.

23. method according to claim 22 is characterized in that, described catalyzer comprises titanium compound and magnesium dihalide, does not contain the inert inorganic oxide carrier.

24., it is characterized in that, described solid catalyst component is added described first polymerization stage and change over to thus in subsequently the step, and do not add other solid catalyst component in described subsequently the step according to claim 22 or 23 described methods.

25. according to any described method among the claim 18-24, it is characterized in that,, preservative coat (C) imposed on the described tube outer surface layer being overlying on described tube outer surface layer (A) before with described coating (B).

26. method according to claim 25 is characterized in that, described coating (B) is being overlying on described preservative coat (C) before, (D) imposes on the described preservative coat with tack coat.

27., it is characterized in that according to any described method among the claim 18-24, described coating (B) is being overlying on described tube outer surface layer (A) before, tack coat (D) is imposed on the described tube outer surface layer.

28., it is characterized in that the ratio M of the weight-average molecular weight of described multimodal ethylene copolymer (B-1) and number-average molecular weight according to any described method among the claim 18-27 _w/ M _nBe 15-50, preferred 20-40, especially 25-40.

29., it is characterized in that the density of described multimodal ethylene copolymer (B-1) is 946-956kg/m according to any described method among the claim 18-28 ³, preferred 946-954kg/m ³

30. according to any described method among the claim 18-29, it is characterized in that the vicat softening temperature of described coating composition (B-2) is at least 117 ℃, more preferably at least 119 ℃, especially preferably at least 120 ℃.

31. according to any described method among the claim 18-30, it is characterized in that, under 60 ℃ and 5MPa, use with ISO 6252:1992 similar methods by CTL (constant stretch load) and to measure, the anti-stress cracking of described coating composition (B-2) is at least 10 hours, preferably at least 15 hours.

32. according to any described method among the claim 18-31, it is characterized in that described coating composition (B-2) is at least 59 according to the shore hardness of ISO 868-2003, preferably at least 60.

33., it is characterized in that the tensile modulus that described coating composition (B-2) is measured according to ISO 572-2 is 800MPa at least according to any described method among the claim 18-32, preferably 850MPa at least.